> A: If you have my book Principles, there’s one about this idea, Prioritize: While you can have virtually anything you want, you can’t have everything you want.

Sounds obvious but if you've ever worked for an organization or with an individual that prioritizes by buckets or labels ('Urgent', 'Extremely Urgent') versus a queue (a Trello column)†, then you've seen how non-obvious and pervasive this can be.

Agreed, a more detailed answer may have been more useful.

†Full disclosure: I have.